JP4820441B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus that collects magnetic resonance signals from a subject.

  As a method of filling data in the (ky, kz) plane of k-space by three-dimensional imaging, there is a method using orthogonal view ordering (see Patent Document 1).

JP 2009-183685 JP

  In orthogonal view ordering, the (ky, kz) plane is divided into segments for each line orthogonal to the kz axis, and data is collected. Therefore, there is a problem that the longer the number of segments, the longer the shooting time. As a method for shortening the photographing time, it is conceivable to include two lines orthogonal to the kz axis in one segment, but this method has a problem that the contrast of the image is lowered.

  In view of the above circumstances, an object of the present invention is to provide a magnetic resonance imaging apparatus capable of obtaining an image with good contrast in a short imaging time.

The magnetic resonance imaging apparatus of the present invention that solves the above problems
A magnetic resonance imaging apparatus that divides a ky-kz plane into z segments and arranges data in each segment,
The ky-kz plane is divided into z center-in areas and z center-out areas by a plurality of lines extending radially from the center of the ky-kz plane,
In the z center-in areas, data is arranged according to a first trajectory that proceeds toward the center of the ky-kz plane,
The z center-out areas are arranged according to a second trajectory that advances in a direction away from the center of the ky-kz plane,
Each of the z segments has a center-in region of the z center-in regions and a center-out region of the z center-out regions,
In each of the z segments, data is arranged in the one center-in area according to the first trajectory, and then data is arranged in the one center-out area according to the second trajectory,
In at least one of the z segments, the angle at the center of the ky-kz plane of the one center-in region is larger than the angle at the center of the ky-kz plane of the one center-out region. It is getting wider.

In the present invention, the angle at the center of the ky-kz plane in the center-out region is wider than the angle at the center of the ky-kz plane in the center-in region. Thereby, since the number of data arranged in one segment can be increased, the total number of segments can be reduced, and the photographing time can be shortened.
Further, by adjusting the number of data included in the center-in area and the center-out area, the timing when data is arranged in the vicinity of the center of the ky-kz plane can be adjusted. It becomes possible.

1 is a schematic diagram of a magnetic resonance imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the imaging | photography site | part in this embodiment. It is a figure which shows the pulse sequence used when imaging | photography the imaging | photography site | part. It is a figure which shows pulse sequence PS and the graph showing the change of the longitudinal magnetization of the structure | tissue of the imaging | photography area | region FOV. It is a figure which shows the relationship between the respiration waveform of the subject 12, and pulse sequence PS. It is a figure which shows the area | region where data are arrange | positioned in k space. It is a figure which shows a mode that the data arrangement | positioning area | region R is divided into two area | regions R1 and R2. It is a figure which shows a mode that each of two area | regions R1 and R2 is divided | segmented into z area | regions. 3 is a diagram illustrating z segments defined in a data arrangement area R. FIG. It is a figure which shows five segments S1, S2, Sx, Sy, and Sz separately among z segments S1-Sz. It is explanatory drawing when arrange | positioning data in the data arrangement | positioning area | region R. FIG. It is a figure which shows a mode that data are arrange | positioned at segments Sx, Sy, and Sz. It is a figure which shows the center area | region most relevant to the contrast of an image in a ky-kz surface. In FIG. 13, it is a figure which shows five segments S1, S2, Sx, Sy, and Sz separately. It is a figure explaining the relationship between the arterial blood 12c and the longitudinal magnetization Mz of the muscle 12e when data are arrange | positioned to inner area | region Ris1 and Ris2 of segment S1. It is a figure which shows the example at the time of dividing | segmenting the data arrangement | positioning area | region R into z = 32 segments. It is a figure which shows the example at the time of dividing | segmenting the data arrangement | positioning area | region R into z = 21 segment. It is a figure which shows the example at the time of dividing | segmenting the data arrangement | positioning area | region R into z = 16 segment. It is the figure which compared and showed the length of the data collection sequence DAQ at the time of dividing | segmenting the data arrangement | positioning area | region R into z = 32 segments, z = 21 segments, and z = 16 segments. It is a figure explaining an imaging result. It is a figure which shows the modification of the shape of a segment. It is a figure which shows the example which divides | segments the rectangular data arrangement area | region R by a segment.

  FIG. 1 is a schematic diagram of a magnetic resonance imaging apparatus according to a first embodiment of the present invention.

  A magnetic resonance imaging apparatus (hereinafter referred to as an MRI (Magnetic Resonance Imaging) apparatus) 1 includes a magnetic field generator 2, a table 3, a receiving coil 4, and the like.

  The magnetic field generator 2 includes a bore 21 in which the subject 12 is accommodated, a superconducting coil 22, a gradient coil 23, and a transmission coil 24. The superconducting coil 22 applies a static magnetic field B0, the gradient coil 23 applies a gradient pulse, and the transmission coil 24 transmits an RF pulse.

  The table 3 has a cradle 31 for transporting the subject 12. The subject 12 is transported to the bore 21 by the cradle 31.

  The receiving coil 4 is attached to the abdomen 12a of the subject 12, and receives a magnetic resonance signal from the abdomen 12a.

  The MRI apparatus 1 further includes a sequencer 5, a transmitter 6, a gradient magnetic field power source 7, a receiver 8, a central processing unit 9, an input device 10, and a display device 11.

  Under the control of the central processing unit 9, the sequencer 5 sends RF pulse information (center frequency, bandwidth, etc.) to the transmitter 6, and gradient magnetic field information (gradient magnetic field strength, etc.) to the gradient magnetic field power supply 7. send.

  The transmitter 6 drives the transmission coil 24 based on the information sent from the sequencer 5.

  The gradient magnetic field power source 7 drives the gradient coil 23 based on the information sent from the sequencer 5.

  The receiver 8 processes the magnetic resonance signal received by the receiving coil 4 and transmits it to the central processing unit 9.

  The central processing unit 9 divides the information of the pulse sequence PS into the sequencer 5 so that the pulse sequence PS for collecting data by dividing the ky-kz plane into a plurality of segments S1 to Sz (see, for example, FIG. 9) is executed. Transmit to. Further, the central processing unit 9 also transmits navigator sequence information for collecting navigator echoes to the sequencer 5 in order to capture the subject 12 by the respiratory synchronization method. Further, the central processing unit 9 summarizes the operations of each unit of the MRI apparatus 1 so as to realize various operations of the MRI apparatus 1 such as reconstructing an image based on the signal received from the receiver 8. The central processing unit 9 is constituted by a computer, for example.

  The input device 10 inputs various commands to the central processing unit 9 according to the operation of the operator 13.

  The display device 11 displays various information.

  The subject 12 is imaged using the MRI apparatus 1 configured as described above.

  FIG. 2 is a diagram showing an imaging region in the present embodiment, and FIG. 3 is a diagram showing a pulse sequence used when imaging the imaging region.

  In the present embodiment, the imaging region FOV includes the abdomen 12 a of the subject 12.

  The pulse sequence PS is a pulse sequence for suppressing the background tissue (for example, venous blood 12d, muscle 12e) of the abdomen 12a and drawing the arterial blood 12c with emphasis. The pulse sequence PS has a selective inversion pulse SIR (Selective Inversion Recovery) and a data acquisition sequence DAQ.

  The selective inversion pulse SIR is a pulse for inverting the longitudinal magnetization of the tissue in the lower region FOV2 located below the heart 12b in the imaging region FOV (see FIG. 2) of the subject 12. The inversion time TI of the selective inversion pulse SIR is set to a time until the longitudinal magnetization of the venous blood 12d reaches the null point. The inversion time TI is a value of about 1 (sec) to 1.5 (sec), for example.

  The data collection sequence DAQ is a sequence for collecting data arranged in k space according to z segments. As the data acquisition sequence DAQ, a gradient echo method sequence or a spin echo method sequence can be used. The time length Td of the data collection sequence DAQ is, for example, about 400 ms to 1500 ms.

  Next, how the longitudinal magnetization of the tissue in the imaging region FOV changes when the imaging region FOV is imaged with the pulse sequence PS will be described.

  FIG. 4 is a diagram showing a pulse sequence PS and a graph representing changes in longitudinal magnetization of the tissue in the imaging region FOV.

  In the graph, two longitudinal magnetization curves are shown. The longitudinal magnetization curve Car represents the time change of longitudinal magnetization of the arterial blood 12c flowing from the heart 12b into the lower region FOV2, and the longitudinal magnetization curve Cmu represents the time change of longitudinal magnetization of the muscle 12e in the lower region FOV2. ing.

  It is assumed that the arterial blood 12c does not yet flow into the lower region FOV2 and exists in the heart 12b at the transmission time t1 of the selective inversion pulse SIR. Therefore, at the transmission time of the selective inversion pulse SIR, the longitudinal magnetization Mz of the arterial blood 12c is Mz = 1. Since the arterial blood 12c from the heart 12b flows into the lower region FOV2 during the inversion time TI, the arterial blood 12c having the longitudinal magnetization Mz = 1 is present in the entire imaging region FOV by the start time t2 of the data acquisition sequence DAQ. Go around.

  On the other hand, the longitudinal magnetization of the muscle 12e in the lower region FOV2 is reversed from Mz = 1 to Mz = −1 at the transmission time t1 of the selective inversion pulse SIR by the selective inversion pulse SIR. Longitudinal magnetization recovery of the muscle 12e progresses during the inversion time TI, and recovers to about Mz = 0.6 by the start time t2 of the data acquisition sequence DAQ. When the data collection sequence DAQ is executed, data is collected from the imaging area FOV. While the data acquisition sequence DAQ is being executed, the longitudinal magnetization Mz of the arterial blood 12c and the muscle 12e gradually decreases. However, since the longitudinal magnetization Mz of the arterial blood 12c is sufficiently larger than the longitudinal magnetization Mz of the muscle 12e, the arterial blood 12c can be drawn with emphasis over the muscle 12e. The inversion time TI is a value set so that the longitudinal magnetization Mz of the venous blood 12d becomes Mz = 0 at the start time t2 of the data acquisition sequence DAQ. Therefore, the arterial blood 12c can be drawn with emphasis from the venous blood 12d.

  Since the imaging region FOV includes the abdomen, it is displaced by breathing. Therefore, if data is collected when body movement due to respiration is large, high-quality images cannot be obtained due to body movement artifacts due to respiration. Therefore, in this embodiment, the subject 12 is imaged by the respiratory synchronization method.

  FIG. 5 is a diagram showing the relationship between the respiratory waveform of the subject 12 and the pulse sequence PS.

  The pulse sequence PS is repeatedly executed in synchronization with the peak of the respiratory waveform Sresp. Therefore, the pulse sequence PS can be executed while the body movement due to respiration is small. By repeatedly executing the pulse sequence PS, data arranged in the k space can be collected.

  Next, how the data is arranged in the k space in the first embodiment will be described. In the first embodiment, the k space is divided into segments. First, how the k space is divided will be described.

  6 to 10 are diagrams for explaining how the k-space is divided into segments in the first embodiment.

  FIG. 6 is a diagram illustrating an area where data is arranged in the k space.

  FIG. 6 shows a ky-kz plane in the k space for convenience of explanation. In the first embodiment, the data arrangement area R has a substantially elliptical shape instead of a rectangular shape. The data arrangement area R is further divided into two areas R1 and R2.

  FIG. 7 is a diagram showing how the data arrangement area R is divided into two areas R1 and R2.

  The data arrangement region R is divided into two regions R1 and R2 by two lines L1 and L2 extending from the center C of the ky-kz plane. The angle β at the center C of the ky-kz plane of the region R2 is wider than the angle α at the center C of the ky-kz plane of the region R1. Each of the two regions R1 and R2 is further divided into z regions.

  FIG. 8 is a diagram illustrating how each of the two regions R1 and R2 is divided into z regions.

  The region R1 is divided into z center-in regions IN1 to INz based on the center C of the ky-kz plane. The center-in areas IN1 to INz are areas in which data is arranged according to the first trajectory Jin that zigzags toward the center C of the ky-kz plane.

  The region R2 is divided into z center-out regions OUT1 to OUTz with the center C of the ky-kz plane as a reference. The center-out areas OUT1 to OUTz are areas in which data is arranged according to the second trajectory Jout that zigzags in a direction away from the center C of the ky-kz plane.

  One center-in area INj (j is an integer from 1 to z) out of z center-in areas IN1 to INz, and one center-out area OUTj (out of z center-out areas OUT1 to OUTz) j = 1 to z), one segment is defined in the data arrangement area R. In FIG. 8, since z center-in areas IN1 to INz and z center-out areas OUT1 to OUTz exist, z segments are defined in the data arrangement area R. Next, z segments defined in the data arrangement area R will be described.

  FIG. 9 is a diagram showing z segments defined in the data arrangement area R.

  In the data arrangement area R, z segments S1 to Sz are defined. The segment Sj (j = 1 to z) is defined by a combination of the center-in area INj and the center-out area OUTj. In FIG. 9, the region of the segment S1 among the z segments S1 to Sz is indicated by a bold line.

  FIG. 10 is a diagram individually showing five segments S1, S2, Sx, Sy, and Sz of z segments S1 to Sz.

The segment S1 (see FIG. 10A) is determined so that the following relationship is established between the vertex angle α1 of the center-in region IN1 and the vertex angle β1 of the center-out region OUT1.
α1 <β1 (1)

That is, the apex angle β1 of the center-out region OUT1 is set to be larger than the apex angle α1 of the center-in region IN1. The reason for this will be described later. In the above description, the relationship between the apex angle α1 of the center-in region IN1 of the segment S1 and the apex angle β1 of the center-out region OUT1 is described. The relationship with the apex angle is the same. For example, in the segment S2, the number “1” in the formula (1) may be replaced with “2”. Therefore, when formula (1) is generalized, it is expressed by the following formula.
αj <βj (2)
j = integer from 1 to z

  The segments S1 to Sz are defined so that the formula (2) is established. Next, how data is arranged in the data arrangement region R divided into the segments S1 to Sz will be described.

  FIG. 11 is an explanatory diagram when data is arranged in the data arrangement area R. FIG.

  FIG. 11A shows a respiratory signal, FIG. 11B shows a pulse sequence PS, and FIG. 11C shows a data arrangement region R on the ky-kz plane.

  In the first pulse sequence PS, data arranged in the segment S1 is collected. The data collection sequence DAQ is divided into a center-in period Pin and a center-out period Pout. In the center-in period Pin, data arranged in the center-in area IN1 of the segment S1 is collected, while in the center-out period Pout, data arranged in the center-out area OUT1 of the segment S1 is collected. In the center-in area IN1, data is arranged according to a trajectory Jin that zigzags toward the center C of the ky-kz plane. In the center-out area OUT1, data is arranged according to a trajectory Jout that zigzags in a direction away from the center C of the ky-kz plane.

  After the data is arranged in the segment S1, the second pulse sequence PS is executed.

  In the second pulse sequence PS, data arranged in the segment S2 is collected. The data collection sequence DAQ is divided into a center-in period Pin and a center-out period Pout. In the center-in period Pin, data arranged in the center-in area IN2 of the segment S2 is collected. On the other hand, in the center-out period Pout, data arranged in the center-out area OUT2 of the segment S2 is collected. In the center-in area IN2, data is arranged according to a trajectory Jin that proceeds zigzag toward the center C of the ky-kz plane. In the center-out area OUT2, data is arranged according to a trajectory Jout that zigzags in a direction away from the center C of the ky-kz plane.

  Similarly, data arranged in the remaining segments S3 to Sz are collected in order.

  FIG. 12 is a diagram illustrating how data is arranged in the segments Sx, Sy, and Sz.

  12A is a diagram showing a respiratory signal, FIG. 12B is a diagram showing a pulse sequence PS, and FIG. 12C is a diagram showing a data arrangement region R on the ky-kz plane.

  In the x-th pulse sequence PS, data arranged in the segment Sx is collected. The data collection sequence DAQ is divided into a center-in period Pin and a center-out period Pout. In the center-in period Pin, data arranged in the center-in area INx of the segment Sx is collected, while in the center-out period Pout, data arranged in the center-out area OUTx of the segment Sx is collected. In the center-in area INx, data is arranged according to a trajectory Jin that zigzags toward the center C of the ky-kz plane. In the center-out area OUT1, data is arranged according to a trajectory Jout that zigzags in a direction away from the center C of the ky-kz plane.

  Similarly, data is also arranged in the segments Sy and Sz. By arranging data in the segment Sz, data is arranged in the entire data arrangement region R.

  By arranging data in the data placement area R according to the method described with reference to FIGS. 11 and 12, in the imaging area FOV (see FIG. 2), the background tissue is suppressed and the arterial blood 12c is highlighted. High contrast images can be obtained. The reason for this will be described below. In the following description, for convenience, the muscle 12e will be described as a background tissue.

  FIG. 13 is a diagram showing a central region most related to the contrast of an image in the ky-kz plane, and FIG. 14 shows five segments S1, S2, Sx, Sy, and Sz individually in FIG. FIG.

  In the ky-kz plane, the region most related to the contrast of the image is a central region Rc that surrounds the center C of the ky-kz plane and the vicinity thereof. Since the segments S1 to Sz cross the central region Rc, the segments S1 to Sz are positioned outside the central region Rc and the inner regions Ris1 and Ris2 positioned inside the central region Rc, as shown in FIG. (In FIG. 14, only the inner regions Ris1 and Ris2 and the outer regions Ros1 and Ros2 of the segments S1, S2, Sx, Sy, and Sz are shown, but other segments are shown. Are also divided into inner regions Ris1 and Ris2 and outer regions Ros1 and Ros2). Therefore, the outer regions Rout1 and Rout2 of the segments S1 to Sz are not so much related to the contrast of the image, but the inner regions Ris1 and Ris2 of the segments S1 to Sz are regions most related to the contrast of the image. For example, in order to obtain a high-contrast image in which the muscle 12e is suppressed and the arterial blood 12c is emphasized, while the value of the longitudinal magnetization difference ΔMz (see FIG. 4) between the muscle 12e and the arterial blood 12c is large, the segments S1 to S1. It is desirable to place data in the inner regions Ris1 and Ris2 of Sz.

  Hereinafter, in the present embodiment, refer to FIG. 15 for the values of the longitudinal magnetization of the muscle 12e and the arterial blood 12c when data is arranged in the inner regions Ris1 and Ris2 of the segments S1 to Sz. While explaining. In the following, the longitudinal magnetization of the muscle 12e and the arterial blood 12c when data is arranged in the inner regions Ris1 and Ris2 will be described for the segment S1, but the other segments S2 to Sz will be described in the same manner as the segment S1. be able to.

  FIG. 15 is a diagram illustrating the relationship between the longitudinal magnetization Mz of the arterial blood 12c and the muscle 12e when data is arranged in the inner regions Ris1 and Ris2 of the segment S1.

  As described with reference to FIG. 11, data is arranged in the center-in period Pin according to the trajectory Jin in the center-in area IN1 of the segment S1. In the center-out area OUT1, data is arranged in the center-out period Pout according to the trajectory Jout. Therefore, in the inner region Ris1, data is arranged in a period P1 from a time point ts in the middle of the center-in period Pin to the end point of the center-in period Pin. In the inner region Ris2, data is arranged in a period P2 from the start time tm of the center-out period Pout to a time point te in the middle of the center-out period Pin. In the periods P1 and P2 in which data is arranged in the inner regions Ris1 and Ris2, the value of ΔMz is about 0.3 to 0.4.

  FIG. 15 illustrates the case where data is arranged in the segment S1, but the other segments S2 to Sz also have a value of about ΔMz = 0.3 to 0.4 similarly to the segment S1. In between, data is arranged in the inner regions Ris1 and Ris2.

  In general, if the value of ΔMz is about 0.3 to 0.4, the MR image can obtain a sufficient contrast between the arterial blood 12c and the muscle 12e. In FIG. 15, only the longitudinal magnetization difference ΔMz between the arterial blood 12c and the muscle 12e is shown, but for example, the longitudinal magnetization difference ΔMz ′ between the arterial blood 12c and the venous blood 12d is also ΔMz ′ = 0.3 to 0. Data is arranged in the inner regions Ris1 and Ris2 while having a value of about .4. Therefore, by arranging data in the segments S1 to Sz according to the trajectories Jin and Jout, it is possible to obtain a high-contrast image in which the background tissue such as the muscle 12e and the venous blood 12d is suppressed and the arterial blood 12c is emphasized.

  When the apex angles α1 to αz of the center-in regions IN1 to INz are increased, the area of the inner region Ris1 is increased. When the apex angles α1 to αz of the center-in regions IN1 to INz are decreased, the area of the inner region Ris1 is decreased. Become. Therefore, by changing the values of the apex angles α1 to αz of the center-in regions IN1 to INz, it is possible to adjust the width of the period P1 in which data is arranged in the inner region Ris1. Similarly, by changing the values of the apex angles β1 to βz of the center-out areas OUT1 to OUTz, the width of the period P2 in which data is arranged in the inner area Ris2 can be adjusted. Therefore, by changing the values of the vertex angles α1 to αz of the center-in regions IN1 to INz and the values of the vertex angles β1 to βz of the center-out regions OUT1 to OUTz, the period P1 and the period P1 and The width of P2 can be adjusted.

  Moreover, in this embodiment, each segment S1-Sz is prescribed | regulated so that the vertex angle of a center out area | region may become a larger value than the vertex angle of a center in area | region (refer Formula (2)). Therefore, since the area of each segment can be increased as compared with the case where αj = βj, the total number of segments defined in the data arrangement region R can be reduced, and the photographing time can be shortened. It becomes. In this embodiment, for all the segments S1 to Sz, the vertex angle of the center-out region is defined to be a value larger than the vertex angle of the center-in region. Only for some segments, the apex angle of the center-out region may be defined to be larger than the apex angle of the center-in region.

  In the above description, the data arrangement area R is divided into z segments. Hereinafter, an example in which the data arrangement area R is divided into z = 32 segments, z = 21 segments, and z = 16 segments will be described.

  16 to 18 are diagrams illustrating an example in which the data arrangement region R is divided into z = 32 segments, z = 21 segments, and z = 16 segments.

  16 to 18, the data arrangement area R is set such that the smaller the total number of segments dividing the data arrangement area R, the narrower the center-in area range A (that is, the wider the center-out area range B). Is divided. Therefore, when the data arrangement area R is divided into z = 16 segments, the range A of the center-in area is the narrowest.

  Next, the length of the data collection sequence DAQ when the data arrangement area R is divided into z = 32 segments, z = 21 segments, and z = 16 segments will be described.

  FIG. 19 shows a comparison of the length of the data collection sequence DAQ when the data arrangement region R is divided into z = 32 segments, z = 21 segments, and z = 16 segments. It is.

  As the total number of segments that divide the data arrangement region R decreases, the area of one segment increases, so that the time of the data collection sequence DAQ can be increased. Therefore, since the number of data points that can be collected in one pulse sequence PS can be increased, the imaging time can be shortened. In FIG. 19, when the total number z of segments is set to z = 16, the data collection sequence DAQ has the longest length L3. Therefore, when the total number z of segments is set to z = 16, the photographing time can be shortened most.

  Further, regardless of the length of the data collection sequence DAQ, L1, L2, and L3, data may be arranged in the central region Rc while the value of ΔMz is about 0.3 to 0.4. Therefore, an image with the same degree of contrast can be obtained regardless of the length of the data acquisition sequence DAQ. In order to verify this, the subject 12 was imaged according to the number of segments shown in FIGS. Hereinafter, the photographing result will be described.

  FIG. 20 is a diagram for explaining a photographing result.

  FIGS. 20A, 20B, and 20C show images obtained by using the method of the present embodiment and photographing conditions thereof. FIG. 20D shows an image obtained when the subject 12 is imaged by orthogonal view ordering and the imaging conditions as a comparative example with the present embodiment.

  The shooting conditions are, in order from the top, (1) the number of segments, (2) the number of data points included in one center-in area, (3) the number of data points included in one center-out area, and (4) the data collection sequence DAQ. Length, (5) shooting time.

  Referring to FIGS. 20A, 20B, and 20C, the shooting times are 2 minutes 17 seconds, 1 minute 30 seconds, and 1 minute 09 seconds. 20A to 20C are compared with FIG. 20D, FIG. 20A shows the same shooting time as FIG. 20D, but FIGS. 20B and 20C. It can be seen that the shooting time is shorter than that in FIG. 20A to 20D, it can be seen that the same contrast is obtained regardless of the shooting time. Therefore, it can be seen that a high-contrast image can be obtained in a short photographing time by using the method of the present embodiment.

  In addition, the shape of the segment which divides | segments the data arrangement | positioning area | region R may be a shape different from FIGS. Next, a modified example of the segment shape will be described.

  FIG. 21 is a diagram showing a modification of the shape of the segment.

  FIG. 21 shows a case where the shape of the segment Sj (j = 1 to z) is substantially a fan shape. The segment Sj has a center-in area INj and a center-out area OUTj. The center-in area INj and the center-out area OUTj are set to be adjacent to each other. Accordingly, in FIG. 21, it is defined that the center-in areas IN1 to INz and the center-out areas OUT1 to OUTz are alternately arranged. Even if the segment Sj is set as shown in FIG. 21, by determining the center-in area INj and the center-out area OUTj so that Expression (2) is established, a high-contrast image can be obtained in a short shooting time. Can do.

  In addition, in the description so far, an example in which the substantially elliptical data arrangement region R is divided into segments has been shown, but the shape of the data arrangement region R is not limited to the substantially elliptical shape, and is arbitrary. Shape is possible.

  FIG. 22 is a diagram illustrating an example of dividing the rectangular data arrangement region R into segments.

  Even if the segment Sj is set as shown in FIG. 22, the center-in area INj and the center-out area OUTj are determined so that the formula (2) is satisfied, thereby obtaining a high-contrast image in a short shooting time. Can do.

  In the present embodiment, a case where the subject 12 is imaged by the respiratory synchronization method is described. However, according to the present invention, when the subject 12 is imaged by the heartbeat synchronization method, the subject 12 is imaged by using both the respiratory synchronization method and the heartbeat synchronization method, and the subject 12 is not used by using the synchronization method. It can also be applied when shooting.

DESCRIPTION OF SYMBOLS 1 MRI apparatus 2 Magnetic field generator 3 Table 4 Reception coil 5 Sequencer 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Central processing unit 10 Input apparatus 11 Display apparatus 12 Subject 13 Operator 22 Superconducting coil 23 Gradient coil 24 Transmitting coil 31 Cradle

Claims (7)

A magnetic resonance imaging apparatus that divides a ky-kz plane into z segments and arranges data in each segment,
The ky-kz plane is divided into z center-in areas and z center-out areas by a plurality of lines extending radially from the center of the ky-kz plane,
In the z center-in areas, data is arranged according to a first trajectory that proceeds toward the center of the ky-kz plane,
The z center-out areas are arranged according to a second trajectory that advances in a direction away from the center of the ky-kz plane,
Each of the z segments has a center-in region of the z center-in regions and a center-out region of the z center-out regions,
In each of the z segments, data is arranged in the one center-in area according to the first trajectory, and then data is arranged in the one center-out area according to the second trajectory,
In at least one of the z segments, the angle at the center of the ky-kz plane of the one center-in region is larger than the angle at the center of the ky-kz plane of the one center-out region. Wide magnetic resonance imaging system.   2. Each of the z segments has an angle at the center of the ky-kz plane of the one center-in region wider than an angle at the center of the ky-kz plane of the one center-out region. The magnetic resonance imaging apparatus described in 1. The ky-kz plane defines a data arrangement area where data is arranged,
The magnetic resonance imaging apparatus according to claim 1, wherein the data arrangement area is divided into the z segments. The ky-kz plane is divided into a first region and a second region,
The z number of center-in regions are provided in the first region,
The magnetic resonance imaging apparatus according to claim 1, wherein the z number of center-out regions is provided in the second region.   The magnetic resonance imaging apparatus according to claim 1, wherein the z center-in regions are alternately arranged with the z center-out regions.   The magnetic resonance imaging apparatus according to claim 1, wherein data is arranged in each of the z segments by a respiratory synchronization method.   The magnetic resonance imaging apparatus according to claim 1, wherein data is arranged in each of the z segments by a heartbeat synchronization method.